This invention relates generally to a method and apparatus for removing a fluid test sample from an electrical cable or the like and further relates to a novel, combination drill and plug that is used with the method and apparatus of this invention.
Electrical cables for the distribution of electrical power are usually manufactured in specific, predetermined lengths. Because of manufacturing limitations and economics, the greater the diameter of the cable the shorter is the length. Consequently, these cables must be connected or spliced end-to-end in order to increase the distance and coverage from the power source beyond that possible with a single length of cable. At lower voltages, splicing poses no real problem, but as the voltage increases, certain precautions must be taken to prevent failure of the splice or joint due to electrical leakage as well as to safeguard personnel from the lethal effects of the electric current. High voltage cables used underground by power companies usually comprise a multiple, usually two or three, of individually insulated conductors which are bound together and which are additionally insulated as a single group. For protection, a lead sheath and/or an insulating and abrasion resisting sheath are additionally placed over the insulated group of conductors.
For underground service, a splice or joint is made by cutting away the sheaths and the insulation for a sufficient distance to permit separation of individually insulated conductors. The insulation is then removed from each conductor for a distance of several inches or just long enough to accept a connecting sleeve which is placed over and crimped onto the bare conductors to form a secure mechanical and electrical joint. The individual splices are then heavily reinsulated using electrical tape, rubber, epoxy-fiberglass, or any other suitable material. A lead sleeve is then positioned so as to surround the splice or joint while leaving a gap between the sleeve and the spliced and insulated conductors. The ends of the sleeve are rounded and formed to fit closely about the lead sheath of the cable and the sleeve and the sheath are soldered together to make a fluid-tight joint. A high quality, dry, electrically insulating oil is then pumped into the sleeve until it is filled completely at which time dry nitrogen gas at low pressure (approximately 3-7 p.s.i.) is introduced into the cable through the combination joint and its associated cables to thereby fill all of the voids. The oil improves the insulating properties of the joint or splice, keeps moisture and air away from the conductors and, in the event of a slight rupture or crack in the joint or cables, will usually seep out, thereby preventing water and air from entering in most cases. However, sometimes water will enter and then will settle in the lowest part of the system, which usually is the joint or splice. When this occurs, the joint insulation degrades and electrical leakage takes place so that the joint or splice eventually fails.
Under previously existing conditions, testing for the presence of water or moisture in the insulating oil required indentifying the suspect joint and cable system, communicating with the distribution center, turning off the current, re-identifying and testing the cable for current and then applying a certification tag to the suspect joint. Only then are the operating personnel permitted to work on the joint or splice.
In order to repair the suspected joint or splice, a hole is first drilled into the sleeve and a quantity of fluid is drained out through the hole. The fluid is collected for later testing and the hole is then plugged with a screw which is soldered to the sleeve to prevent further leakage. After this procedure has been completed, the distribution center is then notified and the power may be turned on. All of the foregoing prior art method is time consuming and costly, requiring many hours, several crews of men and costing thousands of dollars per test.